This contribution presents a new enhanced modeling approach for appendix gap losses for Stirling cycle machines. According to recent findings, previously available models are based on too gross simplifications and require further refinement. It was demonstrated that the flow in the gap is laminar but unsteady, and that existing modeling approaches can be improved by analytical solutions for the flow pattern and the temperature profile in the gap. Assuming locally constant values for the fluid density and the axial temperature gradient, such analytical solutions have been derived as complex functions, accounting for both inertia effects and the correct pressure-driven flow component as imposed by the displacer seal and the mass balance, whereas previous models are impaired by the assumption of plain drag flow. Thus, a refined evaluation of the appendix gap losses was possible. Furthermore, the sum of these losses was found to depend on the axial gap position in case of a constant axial temperature gradient. Because this sum should actually be constant in the adiabatic section of the gap, a curved temperature profile along the gap must be assumed, which corresponds well to previous measurements of the cylinder wall temperature and numerical modeling results. Furthermore, the losses obtained by the new model are larger than those predicted by previous simplified models, and the optimum gap width is shifted to smaller values. Both findings are in good agreement with the expectations based on experimental results.


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    Title :

    New Analytical Model for Appendix Gap Losses in Stirling Cycle Machines


    Contributors:

    Published in:

    Publication date :

    2016-01-11


    Size :

    13 pages




    Type of media :

    Article (Journal)


    Type of material :

    Electronic Resource


    Language :

    English




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